35olds

I've done a few Google searches on this topic and can't find a clear answer - so wondering if anyone here might have any experience they can share.
I'm trying to paint the firewall of my 442 with POR15 Top Coat - Semi Gloss Chassis Black and all the literature (which is very little on the topic) indicates that you don't thin it for spray painting. I've attempted to spray it both straight from the can and also thinned (with the special POR15 Solvent) but I keep getting a "spatter" effect which leaves a somewhat rough (sand paper) surface.
Just wondering if there is some sort of art to spraying this stuff or am I just not thinning it enough ???
Appreciate feedback from anyone with experience here. Thanks.

BackInTheGame

I don't have any POR15 experience, but I've been spraying cars for quite a while. I've seen similar results when I inadvertently had the air pressure up too high. Just a thought...

35olds

Thanks for the feedback. I actually started off using the recommended 25 to 30 PSI range and went down to 20 and up as high as 40 PSI - but no real improvement at any level unfortunately.

Brad J.

I'd ditch the por15 and go with epoxy primer from SPI. Or one of the 2kurethane chassis black from them. SEM makes a hot rod black that works good also. I prefer the epoxy but the others are easier to spray for appearance until you get the hang of epoxy.

Por15 isn't a quality product for restoration. More of a snake oil.

35olds

Thanks Brad, its a great product for frames and its self levelling powers are great but I'm now understanding why there is little to no information from them about spraying - because there is either some sort of down side to thinning it or it won't really work at all. Think I might with a 2K urethane as you suggest. Thanks again.

4speed455

I used por-15 on the inside and outside of my floorboards and firewall. I read reviews of others having issues spraying it so I followed the instructions for painting it on with a brush. It takes a long time to dry so it levels out very well. I ended up with a very consistent finish and little to no brush strokes. I am happy with the results.

Rocketguy

How are you measuring the air pressure? That is important.

What is the ambient temperature, and what range is the POR solvent recommended for?

All paint products are dependent on temperature in one way or another.

You're on the right track with getting the texture correct, and don't forget the gloss is also very important.

Brad J.

Once the POR is applied other coatings don't like to stick to it. It's hard to scratch up for the next coating.

The whole paint over rust is hogwash. I've seen projects where the rust grows right under the coating.

If one goes to the trouble of blasting the project then it's time to upgrade to black epoxy primer and have one product that does it all and looks great.

I had a neighbor come over and blast his suspension parts for a 50's Ford. I offered to shoot them with SPI and he ended up brushing POR over the parts. 4 years later he mentioned the parts are kinda rusty. The car isn't done and the parts were sitting on a shelf in an unheated garage. My 48' Buick has had parts blasted/epoxied sitting in the unheated side for over 8 years and they look like the day I sprayed them.

Only thing good about these moisture cure coatings is marketing. A little harsh but it's the truth.

RetroRanger

IMO POR works fine, but you need to follow the prep instructions ( a real pita) and clean metal helps. You're right despite what it says you can't apply over rust and get lasting results. I did my suspension parts several years ago and the parts still look great. On some trailer parts I brushed the remaining POR 15 right on rust and right on paint, the POR15 did not last at all on that stuff.

35olds

Well the ambient temperature was 70 degrees and humidity about 15% (its Fall here in Australia). I measure air pressure at the gun but unfortunately there is no technical info or data sheets on the POR-15 website and what is there in the FAQ section is very generic with no specific info on Top Coat and nothing on thinning, pressure or humidity.

Brushing it works well but on flat panels like the firewall it's too difficult to get it good enough. Time to move on to 2 pak I think.

Thanks everyone for your feedback

Olds64

Interesting, I have never sprayed POR-15 before but I brushed it on my engine with great results. I was actually considering spraying a POR-15 topcoat over a coat of POR-15 rust converter soon. This thread gives me second thoughts.

Rocketguy

70 degrees is a good temperature for applying most paints.

The correct measurement of air pressure is at the gun, with the trigger squeezed full.

It sounds like your going it right : )

I have never used the POR15 Top Coat - Semi Gloss Chassis Black; I wish I could be of more help.

Good Luck.